Effect of different glycaemic conditions on gene expression of neuropeptides involved in control of food intake in rainbow trout; interaction with stress

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SUMMARYStress conditions induced in rainbow trout a readjustment in the glucosensing response of the hypothalamus and hindbrain such that those sensors did not respond properly to changes in glucose levels, as demonstrated in previous studies. To evaluate the hypothesis that corticotropin-releasing factor (CRF) could be involved in that response, we have incubated the hypothalamus and hindbrain of rainbow trout at different glucose concentrations in the presence of different concentrations of CRF. Under those conditions, we evaluated whether parameters related to glucosensing [the levels of glucose, glycogen and glucose 6-phosphate, the activities of glucokinase (GK), glycogen synthase (GSase) and pyruvate kinase (PK), and mRNA abundance of transcripts for GK, Glut2, Kir.6-like and sulfonylurea receptor (SUR)-like] are modified in the presence of CRF in a way comparable to that observed under stress conditions. We obtained evidence allowing us to suggest that CRF could be involved in the interaction between stress and glucosensing as CRF treatment of the hypothalamus and hindbrain in vitro induced a readjustment in glucosensing parameters similar to that previously observed under stress conditions in vivo. We had also previously demonstrated that stress elicits alterations in food intake in parallel with the readjustment of glucosensing systems. Here, we provide evidence that the mRNA abundance of several of the neuropeptides involved in the regulation of food intake, such as neuropeptide Y (NPY) or cocaine-and amphetamine-regulated transcript (CART), is affected by CRF treatment, in such a way that their expression does not respond to changes in glucose levels in the same way as controls, allowing us to suggest that the food intake response that is integrated by changes in those peptides and known to be reduced by stress could be also mediated by CRF action in glucosensing areas.

Section: Discussion the Effects Of Crf On Glucosensing-related Paramesupporting

confidence: 90%

Section: Gene Expression Analysis By Real-time Quantitative Rt-pcrmentioning

confidence: 99%

CRF treatment induces a readjustment in glucosensing capacity in the hypothalamus and hindbrain of rainbow trout

Conde-Sieira

Librán-Pérez

López‐Patiño

et al. 2011

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“…We also demonstrated that these glucosensing systems are deregulated under stress conditions, like those associated with high stocking density (HSD), resulting in their inability to respond to changes in circulating glucose levels (Conde-Sieira et al, 2010a). Furthermore, the same stress conditions elicit reduced food intake and changes in the mRNA abundance of several peptides related to the control of food intake, including corticotropin-releasing factor (CRF) (Conde-Sieira et al, 2010b), that could be related to the well-known anorectic effect of stress in fish (Wendelaar Bonga, 1997;Bernier, 2006). Accordingly, we have recently demonstrated that the responses to changes in glucose levels of parameters related to glucosensing in the hypothalamus and hindbrain of rainbow trout are modified in the presence of CRF (Conde-Sieira et al, 2011), in a way comparable to that observed under stress conditions (Conde-Sieira et al, 2010a).…”

Section: Introductionmentioning

confidence: 95%

Glucosensing capacity in liver of rainbow trout displays day-night variations possibly related to melatonin action

Conde-Sieira

López‐Patiño

Míguez

et al. 2012

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SUMMARYTo assess whether the glucosensing capacity in peripheral (liver and Brockmann bodies) and central (hypothalamus and hindbrain) locations of rainbow trout displays day-night variations in its response to changes in circulating glucose levels, we evaluated the response of parameters related to glucosensing [glucose, glycogen and glucose 6-phosphate levels, activities of glucokinase (GK), glycogen synthetase (GSase) and pyruvate kinase (PK), and mRNA abundance of GK, glucose transporter 2 (GLUT2), and K ATP channel subunits Kir6.x-like and sulfonylurea receptor (SUR)-like] in fish subjected to hyperglycemic treatment under night or day conditions. No day-night significant variations were noticed in the glucosensing capacity of the hypothalamus, hindbrain and Brockmann bodies. In contrast, a clear differential response was noticed in the liver, where glucose levels, GK activity (and mRNA levels) and GSase activity displayed increased values during the day in hyperglycemic fish compared with controls, and lower (GK mRNA levels) or non-existent (glucose, GK and GSase activities, and Kir6.x-like mRNA levels) values during the night. A similar decrease in parameters related to glucosensing in the liver was observed when fish under day conditions were treated with melatonin, suggesting a modulatory role of melatonin in day-night changes of the glucosensing response in the same tissue.

“…The analyses were carried out with 1 µl cDNA using the MAXIMA SYBR Green qPCR Mastermix (Thermo Scientific, Waltham, MA, USA), in 15 µl of PCR reaction containing 50-500 nmol l −1 of each primer. The mRNA abundance of transcripts of interest (COX4, CPT1c, CPT1d, FBPase, GLUT2, GK, Gnat3, HOAD, Kir6.x-like, LXRα, PK, PPARγ, SGLT-1, SREBP1c, SUR-like, T1R2, T1R3 and UCP2a) was assessed as described in the same species (Panserat et al, 2000(Panserat et al, , 2001Polakof et al, 2008cPolakof et al, , 2011bKolditz et al, 2008;Lansard et al, 2009;Cruz-Garcia et al, 2009;Conde-Sieira et al, 2010;Sánchez-Gurmaches et al, 2012;Polakof and Soengas, 2013;Librán-Pérez et al, 2013). The sequences and accession numbers of the primers used for each transcript are shown in Table 1.…”

Section: Mrna Abundance Analysis By Real-time Quantitative Rt-pcrmentioning

confidence: 99%

In vitro evidence supports the presence of glucokinase-independent glucosensing mechanisms in hypothalamus and hindbrain of rainbow trout

Otero-Rodiño

Velasco

Álvarez-Otero

et al. 2016

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We previously obtained evidence in rainbow trout for the presence and response to changes in circulating levels of glucose (induced by intraperitoneal hypoglycaemic and hyperglycaemic treatments) of glucosensing mechanisms based on liver X receptor (LXR), mitochondrial production of reactive oxygen species (ROS) leading to increased expression of uncoupling protein 2 (UCP2), and sweet taste receptor in the hypothalamus, and on sodium/glucose cotransporter 1 (SGLT-1) in hindbrain. However, these effects of glucose might be indirect. Therefore, we evaluated the response of parameters related to these glucosensing mechanisms in a first experiment using pooled sections of hypothalamus and hindbrain incubated for 6 h at 15°C in modified Hanks' medium containing 2, 4 or 8 mmol l −1 D-glucose. The responses observed in some cases were consistent with glucosensing capacity. In a second experiment, pooled sections of hypothalamus and hindbrain were incubated for 6 h at 15°C in modified Hanks' medium with 8 mmol l −1 D-glucose alone (control) or containing 1 mmol l −1 phloridzin (SGLT-1 antagonist), 20 µmol l −1 genipin (UCP2 inhibitor), 1 µmol l −1 trolox (ROS scavenger), 100 µmol l −1 bezafibrate (T1R3 inhibitor) and 50 µmol l −1 geranyl-geranyl pyrophosphate (LXR inhibitor). The response observed in the presence of these specific inhibitors/ antagonists further supports the proposal that critical components of the different glucosensing mechanisms are functioning in rainbow trout hypothalamus and hindbrain.